Rationalizing the Mechanism of Peroxyformate Decomposition: Computational Insights To Understand Solvent Influence

The heterolytic decomposition of tert-butyl peroxyformate to tert-butanol and carbon dioxide, catalyzed by pyridine, is a long-known example of a reaction whose kinetics are strongly affected by solvent polarity. From DFT and ab initio methods together with the SMD implicit solvation model, an extension on the formerly accepted mechanism is proposed. This novel proposal involves the formation of a carbonic acid ester intermediate and its further decomposition, through an unreported pyridine-mediated stepwise route. Computed barriers for this mechanism at DLPNO/CCSD(T)-def2-TZVP are in excellent agreement with experimental kinetic data across different solvents. Furthermore, the strong relationships between activation energies, geometric parameters in the transition state and the characteristics of the different solvents are also analyzed in depth.